Safety-fuse for electric circuits.



H. G. HERSHEY.

SAFETY FUSE FOR ELECTRIC CIRCUITS.

APPLICATION FILED JAN. 25, 1913.

Patented Jan. 5, 1915.

UNITED STATES PATENT OFFICE.

HERBERT C. HERSHEY, 0F HANOVER, PENNSYLVANIA, ASSIGNOB. T0 N-W EQUIPMENTCO. INC, OF NEW YORK,

N. Y., A CORPORATION OF NEW YORK.

SAFETY-FUSE FOR ELECTRIC CIRCUITS.

Specification of Letters latent.

Patented Jan. 5, 1915.

Application filed January 25, 1913. .Serial No. 744,219.

To all whom it may concern:

Be it known that I, HERBERT O. HERsI-IEY, a citizen of the UnitedStates, and resident of Hanover, in the county of York and State ofPennsylvania, have invented certain new and useful Improvements inSafety-Fuses for Electric Circuits; and I do hereby declare thefollowing to be a full, clear, and exact description of the same,reference being had to the accompanying drawings, forming part of thisspecification, and to the figures and letters of reference markedthereon.

This invention relates to fuses of the type adapted to be included in anelectric circuit, and the fuse member of which is adapted to bedissipated by any excess current through the same, such, for instance,as would be caused by a short circuit beyond the fuse.

The object of the invention is primarily to provide a fuse in which thefuse member may be readily renewed when destroyed by the action of anexcess current, but with which it will be practically impossible tosubstitute for the fuse member a wire or strip of metal which does notpossess the proper characteristics to afiord the desired safety for thecircuit beyond the fuse.

A further object of the invention is to provide a fuse with whichliability of injury either to the fuse structure itself or tosurrounding objects by the formation of an are or high resistance pointin the adjacent members of the fuse shall be reduced to a minimum. i

A further object of the invention is to provide an exceedingly simpleand efiicient structure which may be repaired or a new fuse memberinserted by unskilled labor and without any danger of the parts beingreassembled in such wise as to reduce the efficiency of thc fuse.

The invention consists in certain ,I1OX'6l details of construction andcombinations and arrangements of parts all as will be now described audpointed out particularly in the appended claims. Referring to theaccompanying drawings,Figure 1 is a longitudinal section through a fuseembodying the present improvements. Fig. 2 is a perspective view member.Fig. 3

. cuit terminals,

- is volatilized or melted.

to Fig. 1 through one end of a fuse embodylng the present improvement,but showing a modified and, in some respects, a more desirable form offuse member and clamps. F1g.l.is a perspective view of fuse member ofthe construction embodied in Fig. 3.

Like letters of reference in the several ,figures indicate the sameparts.

In some respects the fuse of the present invention follows the acceptedlines of fuse construction now well understood and therefore n so far asgeneral features of construction are concerned, the illustrations areonly typical of'the application of the invention. F or example the fusemay embody a cylindrical inclosing casing A of vulcanized fiber or othersuitable non-conducting material upon the ends of which caps B aresecured by screw threadsand are adapted to form the terminal members towhich the circuit terminals are connected. As shown,the caps B areprovided with tongues or extensions B adapted to be held betweensuitable clamping devices forming the ciras is customary with devices ofthis kind,particularly where the fuses are of large size and adapted tocarry a heavy current.

The fuse member proper is located within the casing A and is preferablysurrounded by a comminuted or pulverulent material such as asbestos,indicated at C, and vent apertures a may be formed in the casing for theescape of any gases which may be generated at the time the fuse blows orNormally such vent apertures may be closed by a lining such as D, inFig. 1, 'or a covering D, in Fig. 3 which may be of thin papers or of aforaminous material such as netting, all as is customary in the art.

The ends of the casing A are, in accordance with the present invention,preferably provided with tapering internal walls or faces as at A, andadapted for the reception of conical sectional plugs E, E. Between the sctions of the plugs E and E the ends of the fuse member Gr are adaptedto be clamped, the desired clamping action and contact between the partsbeing secured by the pressure exerted by the caps, as they are screwedon to the ends of the casing, and exert a tendency to drive said conicalplugs toward each other.

amperage without rupture, but to be ber G which is adapted to berupturedby the current and L dissi ated' the filling within the casingmay. e ofrelatively narrow and thin construction as illustrated, or of any otherpreferred crosssectional shape, and it will be understood lit'isliproperly proportioned and of ai proper a oy'- to permit of the passageof. a current, of the esired mstantly ruptured and dissipated by thepas' sage of an excess current. At its ends, the

fuse member is preferably made to conform' to the shape of the proximatefaces of the sections of the conical plugs or clamps, and

while these ends may, as shown at the right hand end of Fig. 2, besubstantially flat,

and adapted to be clamped between flat proximate faces of the plugsections, one end at least is preferably made of such conformation as tofit between proximate faces of plug or clamp sections which will be soshaped-as to preclude the possibility of a simple strip of metal or of awire being successfully clamped therebetween, the object being toprevent the substitution of suchordinary devices for a fuse whereby theprejudice and objection to the use of fuses with removable fuse membersis overcome.

As shown in Fig. 2, while the right hand end G of the fuse member G isflat and of extended area so as to be clamped between the proximate flatfaces of the sections E of the plug, the opposite end is provided with arelatively large and tapered central portion G with lateral wings G alladapted to seat in the correspondingly shaped PI'OXI- mate faces of theplug sections E. Each of the plug sections E is for the purpose statedprovided with a central tapered recess 6 rectangular in cross section soas to secure an extended contact surface between the section and fusemember, but at the same time to preclude the successful clamping or useof a device which it might be attempted to substitute for the fusemember, but which is not of the proper conformation.

A construction which is perhaps somewhat better calculated to preventthe possible use of an unauthorized substitute for the fuse member isillustrated in Figs. 3 and 4,

wherein it will be seen that the plug sections, lettered H in thisinstance, are provided in the proximate faces with semi-conical recessesand are adapted for the reception of the conical or frusto-conical end Iof the fuse member 1'. While the opposite end of the fuse member may be,of similar form it is preferably flat as' shown and adapted to beclamped between proximate flat faces of plug sections as shownin Fig. 2.

It will be noted that the conical or tapering formation of the end ofthe fuse member tends, when the plug sections are forced inwardly, toexert an outward pull or'tension on the fuse member itself, thusinsuring a proper seating of the outer face of the end of the fusemember againstthe cap and overcoming a tendency which might ot erwlseexist to buckle the fuse member 3 intermediate its ends. "infuses ofthis general type it has been found in some instances that owingtodefectlve contact between the ends of the fuse member and caps heatwould be generated because of the resistance there oiferedto the passageof the current, or an arc would be formed having a violent heatingefi'ect, resulting in thedestruction of the fuse with the passage of acurrent well within the capacity of the fuse member, or in some instancecausing adjacent objects to be set on fire. With the presentconstruction the liability of such a thing happening is reduced to theminimum, but in order to completely eliminate danger from the causestated, I now coat the contacting faces of the ends of the fuse member,the sections of the plugs, and preferably also the inner faces of thecaps with an easily fusible solder indicated by the shaded areas 9 inFig. 2. The fiat end 'of the fuse member may be provided with openingsor apertures g, into which the solder will run, should any undue heatingoccur. Obviously, with such a construction the first effect of thegeneration of any heat between the contacting members will be to meltthe solder and establish a good electrical and mechanical contact,whereupon the heating will immediately disappear andthe parts willremain in proper effective operative relation. v

In the preferred construction, the cap members 13, in addition to beingfitted on the ends of the casing A by means of screw threads, areprovided with retaining screws K which are passed in through the sidesof the caps, the apertures for the reception of said screws beingaccurately positlonedfas to register properly when the parts have beenadvanced to a point where proper contact will have been established, butwithout exerting any injurious longitudinal pressure on the fuse memberitself. These retaining screws, therefore, constitute a gage forindicating when the parts have been set up to the proper degree and, ofcourse, it will be understood, as incidental thereto that the size andlength of the plug sections and fuse member are properly proportioned toattain the desired ends.

In case a fuse is blown, it is with the presentconstruction, acomparatively simple and inexpensive matter to remove the caps andsubstitute a new fuse member for the one destroyed, and again replacethe parts in position for use, thus overcoming entirely the necessity ofreturning the fuse to the factory or of providing an entirely new fuse.

Having thus described my invention what I claim as new and desire tosecure by Letters latent of the United States, is:

1. In a safety fuse, a non-conducting casing, terminal caps adjustablymounted thereon and closing the ends of the casing, sectional taperingplug members having their larger ends of greater diameter than theinternaldiameter of the ends of the casing mounted in the ends of thecasing with their outer and larger ends beyond the ends of the casing,whereby the sections will be moved toward each other when the caps aremoved inwardly, the proximate faces of the plug sections at one end ofthe casing forming between them a chamber of greater sectional areathanthe body of the fuse, and a fuse member clamped by the plug memberswhen forced inwardly by the caps and having one of its ends enlarged toconform to and filling the said chamber whereby ordinary non-fusiblestrips can not be substituted for the fuse member and clamped inposition.

2. In a safety fuse, a non-conducting casing, terminal caps adjustablymounted thereon and closing the ends of the casing, sectional inwardlytapering plug members having their larger ends of greater diameter thanthe internal diameter of the ends of the casing mounted in the ends ofthe casing with their outer and larger ends in engagement with the capswhereby they are confined in the casing, the proximate faces of thesections of the plug members at one end of the casing having enlargedinwardly tapering recesses therein forming between said sections aninwardly tapering chamber of greater sectional area than the body of thefuse member, and a fuse member clamped by the plug members and havingone of its ends enlarged to conform to the inwardly tapering chamber,said enlarged end being clamped by the plug sections when forcedinwardly by the cap, whereby a longitudinal tension is exerted on thefuse member by the clamping action of the plug sections. In a safetyfuse, a non-conducting casing, a terminal cap adjustably mounted on oneend of the casing, a sectional inwardly tapering plug member having itslarger end of greater diameter than the internal diameter of the end ofthe casing mounted in the said end of the casing with the outer andlarger ends of the sections in engagement with the cap, the proximatefaces of said sections forming between them a chamber of greatersectional area than the body of the fuse, a fuse member having one endenlarged to conform to and filling said chamber, and means for holdingand establishing electrical contact between the opposite end of the fusemember and the terminal cap at that end of the fuse.

4. In a safety fuse, a non-conducting easing, terminal caps adjust-ablymounted thereon-and closing the ends of the casing, a sectional inwardlytapering plug member having its larger end of greater diameter than theinternal diameter of theend of the casing mounted in one end of thecasing with the outer and larger ends of the sections projecting beyondthe /casing for engagement by the cap, the proximate faces of the plugsections being formed with inwardly tapering recesses forming betweenthe sections an inwardly tapering chamber of greater sectional area thanthe body of the fuse, a fuse member having one of its ends enlarged andtapered to conform to and filling the said chamber, and means forholding and estab lishing electrical contact between the opposite end ofthe fuse member and the terminal cap at that end of the fuse.

5. In a safety fuse, a non-conducting casing, terminal caps adj ustablymounted thereon and closing the ends of the casing, sectional inwardlytapering plug members having their larger ends of greater diameter thanthe internal diameter of the ends of the casing mounted in the ends ofthe casing with their outer and larger ends in engagement with the caps,the proximate faces of the sections of one of said plug members havingenlarged recesses therein forming a chamber of greater sectional areathan the body of the fuse member, and the proximate faces of thesections of the other of said plug members being substantially flat, afuse member having its terminals mounted between said plug sections, oneof said terminals being substantially flat to conform to the flatproximate faces of the plug sections at one end of the casing, and theother of said terminals being enlarged to conform to and filling thechamber between the proximate faces of the plug sections at the otherend of the casing.

6. In a safety fuse, a non-conducting casing, terminal caps adjustablymountedthereon and closing the ends of the casing, sectional inwardlytapering plug members having their larger ends of greater diameter thanthe internal diameter of the ends of the casing mounted in the ends ofthe casing with their outer and larger ends in engagement with the caps,the proximate faces of the plug sections at one end of the casing havingenlarged recesses therein of angular formation in cross-section wherebya chamber angular and of greater area in crosssection than the body ofthe fuse is formed between the plug sections, and a fuse member clampedby the plug members and having one of its ends enlarged to conform toand filling the said chamber wherebya strip or wire cannot besubstituted for the fuse member and clamped in position by the sectionsof the plug member.

7. A safety fuse embodying an inclosing sheath, a fusible conductor,metal terminals union of the parts when heated by electric connectedwith the sheath, and having meaction due to defective contact betweenthe 10 fsharglcal clanping K111621118 for the erfids of the parts.

usi e con uctor t e contact ma in surfaces of the terminals beingprovided v vith a HERBERT HERSHEY soldering composition fusible at alower Witnesses: temperature than the fusible conductor EDWARD A.MICHAEL, adapted to effect a mechanical and electrical W. BUSHER.

